1. Field of the Invention
The invention relates to a display device, and more particularly to an array substrate of a display device and a fabrication method thereof.
2. Description of the Related Art
Referring to FIG. 1, a partial top view of an array substrate of a conventional liquid crystal display is shown. Gate lines 12 are formed from a metal layer, data lines 11, a source electrode 11S and a drain electrode 11D are formed from another metal layer. A pixel electrode 14 is formed in a pixel area P defined by any two adjacent gate lines 12 and any two adjacent data lines 11. A passivation layer (not shown) is disposed between the metal layer of the data lines 11, the source electrode 11 S and the drain electrode 11D and the pixel electrode 14. A contact hole 16 is formed in the passivation layer over the drain electrode 11D and the contact hole 16 is filled with the pixel electrode 14 for electrically connecting the drain electrode 11D to the pixel electrode 14.
The drain electrode 11D needs to have a protrudent metal pattern 11P disposed in the pixel area P for disposing the contact hole 16 thereon. However, an aperture ratio of the conventional liquid crystal display is reduced by the protrudent metal pattern 11P of the drain electrode 11D.
Also, in a peripheral area of the array substrate of the conventional liquid crystal display, the metal layer of the gate lines 12 needs to electrically connect to the other metal layer of the data lines 11, the source electrode 11S and the drain electrode 11D, according to the circuit design of the liquid crystal display. There is no overlap between the two metal layers in the peripheral area of the array substrate of the conventional liquid crystal display. Thus, a plurality of contact holes in an insulating layer and the passivation layer over the two metal layers needs to be formed to expose the two metal layers respectively and a transparent electrode material of the pixel electrode 14 is used to fill the plurality of contact holes for electrically connecting the two metal layers at the peripheral area. However, the transparent electrode material of the pixel electrode 14 has a high resistance. Therefore, the resistance of the circuit at the peripheral area of the conventional liquid crystal display is increased.
Moreover, the conventional liquid crystal display includes a color filter (CF) substrate disposed opposite to the array substrate. A plurality of spacers needs to be disposed between the CF substrate and the array substrate for controlling a distance between the two substrates. Generally, the spacers of the conventional liquid crystal display are formed from a photosensitive material on the CF substrate, which is referred to as a spacer on CF (SOC). Therefore, the fabrication of the conventional liquid crystal displays needs a mask and an exposure and a development process to form the SOC.